Why Are Some Icebergs Green? Scientists May Have An Answer
We should all be concerned about Antarctica’s shrinking icebergs. Antarctica’s stunning green icebergs have mystified explorers since they were first found over a century ago. Known to some scientists as “jade bergs” they’re a gorgeous translucent green that resembles the color of old-fashioned soda bottles. They stand apart from the rest of the ocean and delight observers who are used to seeing green in grass or plants but not in an iceberg.
How do they happen and what role do they play in ocean life? Scientists may have finally figured this out.
An Array Of Iceberg Colors
Icebergs can come in a range of colors, most being a variation of blue. There are deeper blue icebergs, baby blue icebergs, and an expected white color. Some may even be striped blue and white together.
We are used to seeing ice from our freezer be relatively clear colored. So, how does the ice generally get its color? As the ice mass grows and changes, compression pushes much of the bubbles out of the structure, changing the light that can be absorbed into it. The more compressed it becomes, the more it absorbs the red rays of light and reflects the shorter blue rays back to our eyes. As a result, the older the ice the more it appears to be blue. Some of the oldest ice can show as turquoise.
Theories About Jade Bergs
So what causes green ice? Scientists have been pondering the question for years. In 1988, Australian glaciologist Steve Warren climbed up on one of the icebergs to get a better look, an act which turned out to be the start of a focused effort to understand what was happening. One of the things that Warren and other scientists have learned is that the structures are made of marine ice, not the glacial ice that is typical for other formations. Marine ice is found underneath ice shelves and is distinctly lacking in air bubbles, something observers had consistently noticed in green ice. This new discovery doesn’t entirely account for the glaciers’ color, however.
For a while, experts believed the color could have something to do with parts of marine animals, plants, and other nutrients that had become a part of the ice. However, when they compared the particle concentration found in these bergs they proved similar to what was found in their blue and white counterparts.
At Last, A New Theory Emerges
Determined to find an answer to this question, a few years ago Steve Warren began to reexamine the green-colored icebergs. This time, his efforts led him in a more productive direction. He followed newer research indicating that the Antarctic ice shelf core, near where the green icebergs were found, contained much higher than expected levels of iron. Warren began to pursue theories related to this research.
His new theory, published in 2019, suggests that this iron is making its way into the ice with its warmer hues of red, oranges, yellows and browns. When these elements are combined with how light was already refracting through the icebergs, darker green tones showed in the icebergs.
Green Ice Helps The Marine Ecosystem
The green ice with it’s higher levels of iron has a distinct benefit for the marine ecosystem. The iron provides nutrients for the microscopic plants that are the basis of the oceanic food web. In a statement accompanying the report, Warren explained it in terms of the icebergs acting as a delivery service that brings much-needed iron and nutrients from Antarctica’s mainland to hungry ocean organisms.
While he wants to do more testing on his theory, Warren is thrilled to have a stronger explanation for the unique ice and to understand its role in Antarctic sea life. Scientists hope that the theory will bolster a continued effort to understand the marine ecosystem in Antarctica and throughout the planet.